A sunroof unit will be explained as an example of an open/close body drive device of a motor vehicle. In the sunroof unit, a slide panel is attached to an opening of a fixed roof and can be moved backward and forward, a rear end of the slide panel can be tilted upward and downward, and the slide panel is connected to and driven by a push-pull cable. The push-pull cable is pushed and pulled by rotating a motor, which has a reduction unit, in a normal direction and a reverse direction, so that the slide panel can be opened and closed. A DC brush motor is usually used as a drive source. The brush motor is rotated by applying electric power via a brush, a rectifying member (commutator) and a relay, and rotation number of the motor is detected by hall ICs so as to control a position of the open/close body.
In case of an open/close body of a motor vehicle, there is a possibility of stopping the open/close body halfway when a motor is stopped due to, for example, failure. Thus, a so-called fail-safe mechanism is provided so as to move the open/close body to a safe position even if the motor is failed. For example, in the sunroof unit, it is impermissible to leave the roof in the open state, so the roof can be closed by manually rotating transmission gears and compulsorily rotating the motor.
These days, noises around an engine have been lowered, and reducing a total noise of a motor vehicle is further required. A motor noise can be lowered to a tolerable level by reducing rotation number of a brush motor. However, the rotation number must be increased to move the open/close body at a high speed, so that a frictional noise between a brush and a commutator is easily generated. Especially, in case that the motor is driven near a user, the moving speed of the open/close body must be lowered so as to reduce the motor noise.
To solve the problem, using a DC brushless motor as a drive source of the open/close body drive device has been studied. In the DC brushless motor, magnetic pole positions of a rotor magnet are detected and electric connection to stator coils is switched, so a plurality of (e.g., three) magnetic pole sensors (hall ICs) are provided. In case of using the brushless motor, rotation number of the motor (the position of the sunroof) and a rotational direction thereof (the moving direction of the sunroof) can be controlled on the basis of detection signals of the hall ICs.